Google: We're killing all file managers in Android Q.
Apple: iPad's file manager gets SMB, unzip, and USB support!
When did I enter an alternate dimension?
File managers still work. Apps are forced to use the Storage Access Framework for accessing shared storage, which means that users can choose the scope for their access. The app can provide a suggestion, but the API is designed to avoid apps from forcing all or nothing access.
The built-in file manager will also still be there, and that's the interface used for selecting file and directories when apps use the Storage Access Framework. It finally gives users control rather than apps requesting full shared storage access and refusing to work otherwise.
That's not an accurate portrayal of SAF. You're misunderstanding what it implements and how it works. An app can request persistent access to a directory tree, which uses the system UI to ask the user to determine access scope. It's entirely usable for implementing file managers.
SAF is a generic file access API. Apps can use as both a client (like a word processor or a file manager) and as a provider (like an app providing access to cloud storage or a network file system). It's not a file manager. It uses the system file manager UI for choosing scope.
So, for example, a file manager will request persistent access to a directory tree. The user can select the root of the volume in the SAF system UI to grant full access to the volume. The file manager now has full, persistent access to that storage volume but it's up to the user.
Any file manager supporting external drives in Android 5.x and 6.x already supports the mechanism used to access shared storage / external drives in Android Q. The same thing applies to other apps. Android 7.x+ added a non-SAF option, but it was flawed and is likely obsolete now.
There are 2 actual complaints:
1) Developers dislike that users are in charge of choosing the scope. One argument is they aren't smart enough to select a volume root for a file manager. It's essentially an argument against user control.
2) The indirection has a performance cost.